M. Shirkhani; Majid Ghaderi; N. Rashidnejad-Omran; R. Mohammadi-Niaei
Abstract
AyQalesi polymetal deposit is located 30 km southeast of Takab in Orumieh-Dokhtar structural zone. For Enzyme LeachSM analysis at the deposit, 723 samples were collected from B-horizon soils. Based on the analytical results and data interpretation, six oxidation anomalies, A through F, have been defined. ...
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AyQalesi polymetal deposit is located 30 km southeast of Takab in Orumieh-Dokhtar structural zone. For Enzyme LeachSM analysis at the deposit, 723 samples were collected from B-horizon soils. Based on the analytical results and data interpretation, six oxidation anomalies, A through F, have been defined. Five of these are recommended as drill targets while one, anomaly C, is not recommended for drilling because it appears to represent a buried intrusion without significant Zn enrichment. Anomalies B, D and E have very high Zn values. For anomaly D, this is because of outcropping Zn mineralization and the presence of mine waste at surface. Anomalies B and E may occur above shallowly buried mineralized zones. Anomalies A, C and F contain much less Zn. Anomaly A may overlie a concealed zone of Zn mineralization that could be buried to a substantial depth. Anomaly F is not recommended for drilling because it appears to be a quite narrow mineralized zone.
A. R. Ghiasvand; M. Ghaderi; N. Rashidnejad-Omran
Abstract
The iron deposits in north of Semnan are located in the south of Central Alborz structural zone. Stratigraphically, the area consists of Paleozoic to Quaternary rock series exposures. The area has been affected by Semnan, Darjazin, Attari and Diktash faults. An intermediate to acidic granitoid body of ...
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The iron deposits in north of Semnan are located in the south of Central Alborz structural zone. Stratigraphically, the area consists of Paleozoic to Quaternary rock series exposures. The area has been affected by Semnan, Darjazin, Attari and Diktash faults. An intermediate to acidic granitoid body of calc-alkaline and metaluminous composition, representing I-type granite characteristics, has intruded the Eocene volcanopyroclastic rocks in the north of Semnan. Skarn development and iron mineralization have occurred at the contact of the intrusive body and the volcanopyroclastic rocks. Mineral Paragenesis consists of magnetite accompanied by hematite, oligist, pyrite, chalcopyrite, garnet, pyroxene and epidote. Geometry of the ore bodies is massive, lenticular and vein type and their texture is disseminated, brecciated, vein-veinlet and massive. Dominant alterations in the area are propylitic, argillic, silicic, sericitic, chloritic and pyritic, respectively. The intrusive body has many similarities with intrusive bodies which form Fe-skarn deposits. Variations in the calculated parameters for REE indicate contribution of magmatic origin hydrothermal fluids to mineralization and that the intrusive body has had the dominant role as source of the skarn ore materials. Along with the intrusion, emplacement and crystallization of intrusive body, Fe-bearing fluids have intruded the volcanopyroclastic rocks, forming sodic metasomatism and deposited iron ores in the north of Semnan which have many similarities with calcic Fe-skarn deposits.
M. Abdi; Majid Ghaderi; N. Rashidnejad-Omran; A. Najafi
Abstract
Two cases of tungsten-copper vein-type mineralization have been studied in the Nezam-abad and Deh-hossein areas, in southwest of Shazand. The hydrothermal quartz-tourmaline mineralized veins have different host rocks (biotitic-granite and meta-sandstone). Considering similar ore metals (tungsten-copper-tin-lead-zinc) ...
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Two cases of tungsten-copper vein-type mineralization have been studied in the Nezam-abad and Deh-hossein areas, in southwest of Shazand. The hydrothermal quartz-tourmaline mineralized veins have different host rocks (biotitic-granite and meta-sandstone). Considering similar ore metals (tungsten-copper-tin-lead-zinc) in the Nezam-abad and Deh-hossein areas, same mineralogy of veins (quartz-dravite) and similar REE variation patterns in the two areas, it is suggested that the Nezam-abad and Deh-hossein mineralized veins have the same origin. It means, when the Br-bearing fluids were active, they caused the quartz-tourmaline vein-type mineralization in this area. Considering the barren intrusions in the area and other mineralogical-geochemical evidences in this study, it could be concluded that tungsten and other metallic elements in the Nezam-abad and Deh-hossein ore-bearing veins have a sedimentary/metamorphic origin.
Gh. R. Rastgoo Moghaddam; E. Rastad; N. Rashid Nejad Omran; M. Mohajel
Abstract
Zartorosht gold deposit is located in southeastern part of the Sanandaj-Sirjan zone. Rock units exposed in the area include mafic to intermediate volcanic series, metamorphosed volcano-sedimentary rocks and meta-basites intruded by basic to felsic dikes. These late ...
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Zartorosht gold deposit is located in southeastern part of the Sanandaj-Sirjan zone. Rock units exposed in the area include mafic to intermediate volcanic series, metamorphosed volcano-sedimentary rocks and meta-basites intruded by basic to felsic dikes. These late Paleozoic units have been metamorphosed under lower to medium green-schist facies. Due to several phases of intense deformation, rock sequence indicates new fabrics. The intensity and types of deformation are not the same in the area, so that rock units illustrate ductile-brittle to brittle shear zones.
Gold mineralization occurs in ductile-brittle and brittle shear zones. In ductile-brittle shear zones, gold mineralization occurs parallel to the foliation with lenticular geometry along the strike and dip of the foliation. Analysis of samples from silicified parts of this zone indicates 0.5 to 7.95 ppm Au. In these zones, deformation fabrics can be observed as primary mylonitization in marginal and middle parts, and brittle fabrics in central parts. Gold mineralization in brittle type shear zones has occurred mainly along N70W to E-W and southern dipping normal faults. This type of mineralization includes gold-bearing veins and siliceous-sulfidic bands and can be followed in a 1.5 km long zone. Au grade in samples from siliceous-sulfidic zone is 17.2 ppm and sometimes it reaches up to 35.7 ppm. Mineralized rock units in shear zones indicate different types of alteration including chloritization, epidotization, sericitization, carbonatization, argilization, silicification and sulfidization. Siliceous-sulfidic alteration corresponds to ore-bearing zones within the shear zones.
Studies suggested temporal and spatial relation between alteration and deformation. Spatial relation is explained by overlapping alteration and deformation zones. Foliation parallel open spaces (generated during ductile deformation and mineralization processes) and also micro-fractures in porphyroclasts (generated during grain cataclastic flow) have been filled with hydrothermal - stage quartz and pyrite indicating temporal correlation of alteration and deformation. Au grade changes have close relation with deformation and alteration intensity. This relation has been distinguished by analysis of samples taken from trenches and tunnels perpendicular or parallel to general foliation of rock units. High gold content is related to intensely deformed (mylonitic and ultracataclasite) siliceous and sulfidic parts and Au-bearing siliceous-sulfidic parts coinciding with the inner parts of alteration zones.
Ore-mineral assemblages in the area are relatively simple including pyrite, arsenian-pyrite, rarely galena and sphalerite. Based on microscopic studies, Au occurs as free grains and electrum. Also electron-microprobe and electron-microscope analysis indicate that at least some of Au grains are in sulfide minerals lattice. According to these studies, gold has been observed with both pyrite and arsenian-pyrite phases. Ag has also been detected in sulfide minerals lattice and siliceous gangue.
Controlling parameters for mineral concentration in Zartorosht deposit are shear zones (ductile-brittle and brittle) and alteration (silicification and sulfidization). Based on the comparison of Zartorosht main characteristics with orogenic gold deposits, Zartorosht has the most similarities with orogenic gold mineralization; therefore, it is considered to be of this type.